status-im/nimPNG
2
0
Fork 0
mirror of https://github.com/status-im/nimPNG.git synced 2025-02-18 07:26:32 +00:00
Code Issues Projects Releases Wiki Activity

Merge pull request #46 from jangko/new_api

Browse Source 
New API, fixes #36
This commit is contained in:
andri lim 2020-06-05 15:49:50 +07:00 committed by GitHub
commit ed12086325
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 1082 additions and 187 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
apidoc.md Normal file
View File

@ -0,0 +1,61 @@
## Legacy API
```Nim
proc encodePNG*(input: string, colorType: PNGColorType, bitDepth, w, h: int, settings = PNGEncoder(nil)): PNG
proc encodePNG32*(input: string, w, h: int): PNG
proc encodePNG24*(input: string, w, h: int): PNG
when not defined(js):
proc savePNG*(fileName, input: string, colorType: PNGColorType, bitDepth, w, h: int): bool
proc savePNG32*(fileName, input: string, w, h: int): bool
proc savePNG24*(fileName, input: string, w, h: int): bool
proc prepareAPNG*(colorType: PNGColorType, bitDepth, numPlays: int, settings = PNGEncoder(nil)): PNG
proc prepareAPNG24*(numPlays = 0): PNG
proc prepareAPNG32*(numPlays = 0): PNG
proc addDefaultImage*(png: PNG, input: string, width, height: int, ctl = APNGFrameControl(nil)): bool
proc addFrame*(png: PNG, frame: string, ctl: APNGFrameControl): bool
proc encodeAPNG*(png: PNG): string
when not defined(js):
proc saveAPNG*(png: PNG, fileName: string): bool
proc decodePNG*(s: Stream, colorType: PNGColorType, bitDepth: int, settings = PNGDecoder(nil)): PNGResult
proc decodePNG*(s: Stream, settings = PNGDecoder(nil)): PNG
when not defined(js):
proc loadPNG*(fileName: string, colorType: PNGColorType, bitDepth: int, settings: PNGDecoder = nil): PNGResult
proc loadPNG32*(fileName: string, settings = PNGDecoder(nil)): PNGResult
proc loadPNG24*(fileName: string, settings = PNGDecoder(nil)): PNGResult
proc decodePNG32*(input: string, settings = PNGDecoder(nil)): PNGResult
proc decodePNG24*(input: string, settings = PNGDecoder(nil)): PNGResult
```
## New API
```Nim
proc decodePNG*(T: type, s: Stream, colorType: PNGColorType, bitDepth: int, settings = PNGDecoder(nil)): PNGResult[T]
proc decodePNG*(T: type, s: Stream, settings = PNGDecoder(nil)): PNG
type
PNGRes*[T] = Result[PNGResult[T], string]
when not defined(js):
proc loadPNG*(T: type, fileName: string, colorType: PNGColorType, bitDepth: int, settings: PNGDecoder = nil): PNGRes[T]
proc loadPNG32*(T: type, fileName: string, settings = PNGDecoder(nil)): PNGRes[T]
proc loadPNG24*(T: type, fileName: string, settings = PNGDecoder(nil)): PNGRes[T]
proc decodePNG32*(T: type, input: T, settings = PNGDecoder(nil)): PNGRes[T]
proc decodePNG24*(T: type, input: T, settings = PNGDecoder(nil)): PNGRes[T]
```
## How to use PNGRes?
```Nim
let res = loadPNG32(seq[uint8], fileName, settings)
if res.isOk: result = res.get() # get PNGResult[seq[uint8]]
else: debugEcho res.error() # get error string
```

506
nimPNG.nim
View File

File diff suppressed because it is too large Load Diff

2
nimPNG.nimble
View File

@ -1,5 +1,5 @@
# Package # Package
version = "0.2.7" version = "0.3.0"
author = "Andri Lim" author = "Andri Lim"
description = "PNG encoder and decoder" description = "PNG encoder and decoder"
license = "MIT" license = "MIT"

642
nimPNG/results.nim Normal file
View File

@ -0,0 +1,642 @@
# nim-result is also available stand-alone from https://github.com/arnetheduck/nim-result/
# Copyright (c) 2019 Jacek Sieka
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
type
ResultError*[E] = object of ValueError
## Error raised when using `tryGet` value of result when error is set
## See also Exception bridge mode
error*: E
ResultDefect* = object of Defect
## Defect raised when accessing value when error is set and vice versa
## See also Exception bridge mode
Result*[T, E] = object
## Result type that can hold either a value or an error, but not both
##
## # Example
##
## ```
## # It's convenient to create an alias - most likely, you'll do just fine
## # with strings or cstrings as error
##
## type R = Result[int, string]
##
## # Once you have a type, use `ok` and `err`:
##
## func works(): R =
## # ok says it went... ok!
## R.ok 42
## func fails(): R =
## # or type it like this, to not repeat the type!
## result.err "bad luck"
##
## if (let w = works(); w.isOk):
## echo w[], " or use value: ", w.value
##
## # In case you think your callers want to differentiate between errors:
## type
## Error = enum
## a, b, c
## type RE[T] = Result[T, Error]
##
## # In the expriments corner, you'll find the following syntax for passing
## # errors up the stack:
## func f(): R =
## let x = ?works() - ?fails()
## assert false, "will never reach"
##
## # If you provide this exception converter, this exception will be raised
## # on dereference
## func toException(v: Error): ref CatchableError = (ref CatchableError)(msg: $v)
## try:
## RE[int].err(a)[]
## except CatchableError:
## echo "in here!"
##
## ```
##
## See the tests for more practical examples, specially when working with
## back and forth with the exception world!
##
## # Potential benefits:
##
## * Handling errors becomes explicit and mandatory at the call site -
## goodbye "out of sight, out of mind"
## * Errors are a visible part of the API - when they change, so must the
## calling code and compiler will point this out - nice!
## * Errors are a visible part of the API - your fellow programmer is
## reminded that things actually can go wrong
## * Jives well with Nim `discard`
## * Jives well with the new Defect exception hierarchy, where defects
## are raised for unrecoverable errors and the rest of the API uses
## results
## * Error and value return have similar performance characteristics
## * Caller can choose to turn them into exceptions at low cost - flexible
## for libraries!
## * Mostly relies on simple Nim features - though this library is no
## exception in that compiler bugs were discovered writing it :)
##
## # Potential costs:
##
## * Handling errors becomes explicit and mandatory - if you'd rather ignore
## them or just pass them to some catch-all, this is noise
## * When composing operations, value must be lifted before processing,
## adding potential verbosity / noise (fancy macro, anyone?)
## * There's no call stack captured by default (see also `catch` and
## `capture`)
## * The extra branching may be more expensive for the non-error path
## (though this can be minimized with PGO)
##
## The API visibility issue of exceptions can also be solved with
## `{.raises.}` annotations - as of now, the compiler doesn't remind
## you to do so, even though it knows what the right annotation should be.
## `{.raises.}` does not participate in generic typing, making it just as
## verbose but less flexible in some ways, if you want to type it out.
##
## Many system languages make a distinction between errors you want to
## handle and those that are simply bugs or unrealistic to deal with..
## handling the latter will often involve aborting or crashing the funcess -
## reliable systems like Erlang will try to relaunch it.
##
## On the flip side we have dynamic languages like python where there's
## nothing exceptional about exceptions (hello StopIterator). Python is
## rarely used to build reliable systems - its strengths lie elsewhere.
##
## # Exception bridge mode
##
## When the error of a `Result` is an `Exception`, or a `toException` helper
## is present for your error type, the "Exception bridge mode" is
## enabled and instead of raising `ResultError`, `tryGet` will raise the
## given `Exception` on access. `[]` and `get` will continue to raise a
## `Defect`.
##
## This is an experimental feature that may be removed.
##
## # Other languages
##
## Result-style error handling seems pretty popular lately, specially with
## statically typed languages:
## Haskell: https://hackage.haskell.org/package/base-4.11.1.0/docs/Data-Either.html
## Rust: https://doc.rust-lang.org/std/result/enum.Result.html
## Modern C++: https://github.com/viboes/std-make/tree/master/doc/proposal/expected
## More C++: https://github.com/ned14/outcome
##
## Swift is interesting in that it uses a non-exception implementation but
## calls errors exceptions and has lots of syntactic sugar to make them feel
## that way by implicitly passing them up the call chain - with a mandatory
## annotation that function may throw:
## https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html
##
## # Considerations for the error type
##
## * Use a `string` or a `cstring` if you want to provide a diagnostic for
## the caller without an expectation that they will differentiate between
## different errors. Callers should never parse the given string!
## * Use an `enum` to provide in-depth errors where the caller is expected
## to have different logic for different errors
## * Use a complex type to include error-specific meta-data - or make the
## meta-data collection a visible part of your API in another way - this
## way it remains discoverable by the caller!
##
## A natural "error API" progression is starting with `Option[T]`, then
## `Result[T, cstring]`, `Result[T, enum]` and `Result[T, object]` in
## escalating order of complexity.
##
## # Other implemenations in nim
##
## There are other implementations in nim that you might prefer:
## * Either from nimfp: https://github.com/vegansk/nimfp/blob/master/src/fp/either.nim
## * result_type: https://github.com/kapralos/result_type/
##
## # Implementation notes
##
## This implementation is mostly based on the one in rust. Compared to it,
## there are a few differences - if know of creative ways to improve things,
## I'm all ears.
##
## * Rust has the enum variants which lend themselves to nice construction
## where the full Result type isn't needed: `Err("some error")` doesn't
## need to know value type - maybe some creative converter or something
## can deal with this?
## * Nim templates allow us to fail fast without extra effort, meaning the
## other side of `and`/`or` isn't evaluated unless necessary - nice!
## * Rust uses From traits to deal with result translation as the result
## travels up the call stack - needs more tinkering - some implicit
## conversions would be nice here
## * Pattern matching in rust allows convenient extraction of value or error
## in one go.
##
## # Performance considerations
##
## When returning a Result instead of a simple value, there are a few things
## to take into consideration - in general, we are returning more
## information directly to the caller which has an associated cost.
##
## Result is a value type, thus its performance characteristics
## generally follow the performance of copying the value or error that
## it stores. `Result` would benefit greatly from "move" support in the
## language.
##
## In many cases, these performance costs are negligeable, but nonetheless
## they are important to be aware of, to structure your code in an efficient
## manner:
##
## * Memory overhead
## Result is stored in memory as a union with a `bool` discriminator -
## alignment makes it somewhat tricky to give an exact size, but in
## general, `Result[int, int]` will take up `2*sizeof(int)` bytes:
## 1 `int` for the discriminator and padding, 1 `int` for either the value
## or the error. The additional size means that returning may take up more
## registers or spill onto the stack.
## * Loss of RVO
## Nim does return-value-optimization by rewriting `proc f(): X` into
## `proc f(result: var X)` - in an expression like `let x = f()`, this
## allows it to avoid a copy from the "temporary" return value to `x` -
## when using Result, this copy currently happens always because you need
## to fetch the value from the Result in a second step: `let x = f().value`
## * Extra copies
## To avoid spurious evaluation of expressions in templates, we use a
## temporary variable sometimes - this means an unnecessary copy for some
## types.
## * Bad codegen
## When doing RVO, Nim generates poor and slow code: it uses a construct
## called `genericReset` that will zero-initialize a value using dynamic
## RTTI - a process that the C compiler subsequently is unable to
## optimize. This applies to all types, but is exacerbated with Result
## because of its bigger footprint - this should be fixed in compiler.
## * Double zero-initialization bug
## Nim has an initialization bug that causes additional poor performance:
## `var x = f()` will be expanded into `var x; zeroInit(x); f(x)` where
## `f(x)` will call the slow `genericReset` and zero-init `x` again,
## unnecessarily.
##
## Comparing `Result` performance to exceptions in Nim is difficult - it
## will depend on the error type used, the frequency at which exceptions
## happen, the amount of error handling code in the application and the
## compiler and backend used.
##
## * the default C backend in nim uses `setjmp` for exception handling -
## the relative performance of the happy path will depend on the structure
## of the code: how many exception handlers there are, how much unwinding
## happens. `setjmp` works by taking a snapshot of the full CPU state and
## saving it to memory when enterting a try block (or an implict try
## block, such as is introduced with `defer` and similar constructs).
## * an efficient exception handling mechanism (like the C++ backend or
## `nlvm`) will usually have a lower cost on the happy path because the
## value can be returned more efficiently. However, there is still a code
## and data size increase depending on the specific situation, as well as
## loss of optimization opportunities to consider.
## * raising an exception is usually (a lot) slower than returning an error
## through a Result - at raise time, capturing a call stack and allocating
## memory for the Exception is expensive, so the performance difference
## comes down to the complexity of the error type used.
## * checking for errors with Result is local branching operation that also
## happens on the happy path - this may be a cost.
##
## An accurate summary might be that Exceptions are at its most efficient
## when errors are not handled and don't happen.
##
## # Relevant nim bugs
##
## https://github.com/nim-lang/Nim/issues/13799 - type issues
## https://github.com/nim-lang/Nim/issues/8745 - genericReset slow
## https://github.com/nim-lang/Nim/issues/13879 - double-zero-init slow
## https://github.com/nim-lang/Nim/issues/14318 - generic error raises pragma
case o: bool
of false:
e: E
of true:
v: T
Opt*[T] = Result[T, void]
func raiseResultError[T, E](self: Result[T, E]) {.noreturn, noinline.} =
# noinline because raising should take as little space as possible at call
# site
mixin toException
when E is ref Exception:
if self.e.isNil: # for example Result.default()!
raise (ref ResultError[void])(msg: "Trying to access value with err (nil)")
raise self.e
elif compiles(toException(self.e)):
raise toException(self.e)
elif compiles($self.e):
raise (ref ResultError[E])(
error: self.e, msg: "Trying to access value with err: " & $self.e)
else:
raise (res ResultError[E])(msg: "Trying to access value with err", error: self.e)
func raiseResultDefect(m: string, v: auto) {.noreturn, noinline.} =
mixin `$`
when compiles($v): raise (ref ResultDefect)(msg: m & ": " & $v)
else: raise (ref ResultDefect)(msg: m)
func raiseResultDefect(m: string) {.noreturn, noinline.} =
raise (ref ResultDefect)(msg: m)
template assertOk(self: Result) =
if not self.o:
when self.E isnot void:
raiseResultDefect("Trying to acces value with err Result", self.e)
else:
raiseResultDefect("Trying to acces value with err Result")
template ok*[T, E](R: type Result[T, E], x: auto): R =
## Initialize a result with a success and value
## Example: `Result[int, string].ok(42)`
R(o: true, v: x)
template ok*[T, E](self: var Result[T, E], x: auto) =
## Set the result to success and update value
## Example: `result.ok(42)`
self = ok(type self, x)
template err*[T, E](R: type Result[T, E], x: auto): R =
## Initialize the result to an error
## Example: `Result[int, string].err("uh-oh")`
R(o: false, e: x)
template err*[T](R: type Result[T, void]): R =
R(o: false)
template err*[T, E](self: var Result[T, E], x: auto) =
## Set the result as an error
## Example: `result.err("uh-oh")`
self = err(type self, x)
template err*[T](self: var Result[T, void]) =
## Set the result as an error
## Example: `result.err()`
self = err(type self)
template ok*(v: auto): auto = ok(typeof(result), v)
template err*(v: auto): auto = err(typeof(result), v)
template isOk*(self: Result): bool = self.o
template isErr*(self: Result): bool = not self.o
template isSome*(o: Opt): bool =
## Alias for `isOk`
isOk o
template isNone*(o: Opt): bool =
## Alias of `isErr`
isErr o
func map*[T, E, A](
self: Result[T, E], f: proc(x: T): A): Result[A, E] {.inline.} =
## Transform value using f, or return error
##
## ```
## let r = Result[int, cstring).ok(42)
## assert r.map(proc (v: int): int = $v).get() == "42"
## ```
if self.o: result.ok(f(self.v))
else: result.err(self.e)
func flatMap*[T, E, A](
self: Result[T, E], f: proc(x: T): Result[A, E]): Result[A, E] {.inline.} =
if self.o: f(self.v)
else: Result[A, E].err(self.e)
func mapErr*[T: not void, E, A](
self: Result[T, E], f: proc(x: E): A): Result[T, A] {.inline.} =
## Transform error using f, or return value
if self.o: result.ok(self.v)
else: result.err(f(self.e))
func mapConvert*[T0, E0](
self: Result[T0, E0], T1: type): Result[T1, E0] {.inline.} =
## Convert result value to A using an conversion
# Would be nice if it was automatic...
if self.o: result.ok(T1(self.v))
else: result.err(self.e)
func mapCast*[T0, E0](
self: Result[T0, E0], T1: type): Result[T1, E0] {.inline.} =
## Convert result value to A using a cast
## Would be nice with nicer syntax...
if self.o: result.ok(cast[T1](self.v))
else: result.err(self.e)
template `and`*[T0, E, T1](self: Result[T0, E], other: Result[T1, E]): Result[T1, E] =
## Evaluate `other` iff self.isOk, else return error
## fail-fast - will not evaluate other if a is an error
let s = self
if s.o:
other
else:
when type(self) is type(other):
s
else:
type R = type(other)
err(R, s.e)
template `or`*[T, E0, E1](self: Result[T, E0], other: Result[T, E1]): Result[T, E1] =
## Evaluate `other` iff `not self.isOk`, else return `self`
## fail-fast - will not evaluate `other` if `self` is ok
##
## ```
## func f(): Result[int, SomeEnum] =
## f2() or err(EnumValue) # Collapse errors from other module / function
## ```
let s = self
if s.o:
when type(self) is type(other):
s
else:
type R = type(other)
ok(R, s.v)
else:
other
template catch*(body: typed): Result[type(body), ref CatchableError] =
## Catch exceptions for body and store them in the Result
##
## ```
## let r = catch: someFuncThatMayRaise()
## ```
type R = Result[type(body), ref CatchableError]
try:
R.ok(body)
except CatchableError as e:
R.err(e)
template capture*[E: Exception](T: type, someExceptionExpr: ref E): Result[T, ref E] =
## Evaluate someExceptionExpr and put the exception into a result, making sure
## to capture a call stack at the capture site:
##
## ```
## let e: Result[void, ValueError] = void.capture((ref ValueError)(msg: "test"))
## echo e.error().getStackTrace()
## ```
type R = Result[T, ref E]
var ret: R
try:
# TODO is this needed? I think so, in order to grab a call stack, but
# haven't actually tested...
if true:
# I'm sure there's a nicer way - this just works :)
raise someExceptionExpr
except E as caught:
ret = R.err(caught)
ret
func `==`*[T0, E0, T1, E1](lhs: Result[T0, E0], rhs: Result[T1, E1]): bool {.inline.} =
if lhs.o != rhs.o:
false
elif lhs.o: # and rhs.o implied
lhs.v == rhs.v
else:
lhs.e == rhs.e
func get*[T: not void, E](self: Result[T, E]): T {.inline.} =
## Fetch value of result if set, or raise Defect
## Exception bridge mode: raise given Exception instead
## See also: Option.get
assertOk(self)
self.v
func tryGet*[T: not void, E](self: Result[T, E]): T {.inline.} =
## Fetch value of result if set, or raise
## When E is an Exception, raise that exception - otherwise, raise a ResultError[E]
mixin raiseResultError
if not self.o: self.raiseResultError()
self.v
func get*[T, E](self: Result[T, E], otherwise: T): T {.inline.} =
## Fetch value of result if set, or return the value `otherwise`
## See `valueOr` for a template version that avoids evaluating `otherwise`
## unless necessary
if self.o: self.v
else: otherwise
func get*[T, E](self: var Result[T, E]): var T {.inline.} =
## Fetch value of result if set, or raise Defect
## Exception bridge mode: raise given Exception instead
## See also: Option.get
assertOk(self)
self.v
template `[]`*[T: not void, E](self: Result[T, E]): T =
## Fetch value of result if set, or raise Defect
## Exception bridge mode: raise given Exception instead
mixin get
self.get()
template `[]`*[T, E](self: var Result[T, E]): var T =
## Fetch value of result if set, or raise Defect
## Exception bridge mode: raise given Exception instead
mixin get
self.get()
template unsafeGet*[T, E](self: Result[T, E]): T =
## Fetch value of result if set, undefined behavior if unset
## See also: Option.unsafeGet
assert self.o
self.v
func expect*[T: not void, E](self: Result[T, E], m: string): T =
## Return value of Result, or raise a `Defect` with the given message - use
## this helper to extract the value when an error is not expected, for example
## because the program logic dictates that the operation should never fail
##
## ```nim
## let r = Result[int, int].ok(42)
## # Put here a helpful comment why you think this won't fail
## echo r.expect("r was just set to ok(42)")
## ```
if not self.o:
raiseResultDefect(m, self.e)
self.v
func expect*[T: not void, E](self: var Result[T, E], m: string): var T =
if not self.o:
raiseResultDefect(m, self.e)
self.v
func `$`*(self: Result): string =
## Returns string representation of `self`
if self.o: "Ok(" & $self.v & ")"
else: "Err(" & $self.e & ")"
func error*[T, E](self: Result[T, E]): E =
## Fetch error of result if set, or raise Defect
if self.o:
when T is not void:
raiseResultDefect("Trying to access error when value is set", self.v)
else:
raise (ref ResultDefect)(msg: "Trying to access error when value is set")
self.e
template value*[T, E](self: Result[T, E]): T =
mixin get
self.get()
template value*[T, E](self: var Result[T, E]): T =
mixin get
self.get()
template valueOr*[T, E](self: Result[T, E], def: T): T =
## Fetch value of result if set, or supplied default
## default will not be evaluated iff value is set
if self.o: self.v
else: def
# void support
template ok*[E](R: type Result[void, E]): auto =
## Initialize a result with a success and value
## Example: `Result[int, string].ok(42)`
R(o: true)
template ok*[E](self: var Result[void, E]) =
## Set the result to success and update value
## Example: `result.ok(42)`
mixin ok
self = (type self).ok()
template ok*(): auto =
mixin ok
ok(typeof(result))
template err*(): auto =
mixin err
err(typeof(result))
# TODO:
# Supporting `map` and `get` operations on a `void` result is quite
# an unusual API. We should provide some motivating examples.
func map*[E, A](
self: Result[void, E], f: proc(): A): Result[A, E] {.inline.} =
## Transform value using f, or return error
if self.o: result.ok(f())
else: result.err(self.e)
func flatMap*[E, A](
self: Result[void, E], f: proc(): Result[A, E]): Result[A, E] {.inline.} =
if self.o: f(self.v)
else: Result[A, E].err(self.e)
func mapErr*[E, A](
self: Result[void, E], f: proc(x: E): A): Result[void, A] {.inline.} =
## Transform error using f, or return value
if self.o: result.ok()
else: result.err(f(self.e))
func map*[T, E](
self: Result[T, E], f: proc(x: T)): Result[void, E] {.inline.} =
## Transform value using f, or return error
if self.o: f(self.v); result.ok()
else: result.err(self.e)
func get*[E](self: Result[void, E]) {.inline.} =
## Fetch value of result if set, or raise
## See also: Option.get
mixin assertOk
assertOk(self)
func tryGet*[E](self: Result[void, E]) {.inline.} =
## Fetch value of result if set, or raise a CatchableError
mixin raiseResultError
if not self.o:
self.raiseResultError()
template `[]`*[E](self: Result[void, E]) =
## Fetch value of result if set, or raise
mixin get
self.get()
template unsafeGet*[E](self: Result[void, E]) =
## Fetch value of result if set, undefined behavior if unset
## See also: Option.unsafeGet
assert self.o
func expect*[E](self: Result[void, E], msg: string) =
if not self.o:
raise (ref ResultDefect)(msg: msg)
func `$`*[E](self: Result[void, E]): string =
## Returns string representation of `self`
if self.o: "Ok()"
else: "Err(" & $self.e & ")"
template value*[E](self: Result[void, E]) =
mixin get
self.get()
template value*[E](self: var Result[void, E]) =
mixin get
self.get()
template `?`*[T, E](self: Result[T, E]): T =
## Early return - if self is an error, we will return from the current
## function, else we'll move on..
##
## ```
## let v = ? funcWithResult()
## echo v # prints value, not Result!
## ```
## Experimental
# TODO the v copy is here to prevent multiple evaluations of self - could
# probably avoid it with some fancy macro magic..
let v = (self)
if not v.o:
when typeof(result) is typeof(v):
return v
else:
return err(typeof(result), v.e)
v.v

42
readme.md
View File

@ -1,6 +1,10 @@
# nimPNG (PNG + APNG) # nimPNG (PNG + APNG)
Portable Network Graphics Encoder and Decoder written in Nim store lossless image with good compression. Portable Network Graphics Encoder and Decoder written in Nim store lossless image with good compression.
Since version 0.2.0 also support Animated PNG!
Notable releases:
- 0.2.0 support Animated PNG!
- 0.2.6 compile with --gc:arc.
- 0.3.0 [new set of API](apidoc.md) using seq[uint8] and new method to handle error.
[![Build Status (Travis)](https://img.shields.io/travis/jangko/nimPNG/master.svg?label=Linux%20/%20macOS "Linux/macOS build status (Travis)")](https://travis-ci.org/jangko/nimPNG) [![Build Status (Travis)](https://img.shields.io/travis/jangko/nimPNG/master.svg?label=Linux%20/%20macOS "Linux/macOS build status (Travis)")](https://travis-ci.org/jangko/nimPNG)
[![Build status](https://ci.appveyor.com/api/projects/status/7ap5r5a41t7ea04p?svg=true)](https://ci.appveyor.com/project/jangko/nimpng) [![Build status](https://ci.appveyor.com/api/projects/status/7ap5r5a41t7ea04p?svg=true)](https://ci.appveyor.com/project/jangko/nimpng)
@ -9,11 +13,11 @@ Since version 0.2.0 also support Animated PNG!
all PNG standard color mode are supported: all PNG standard color mode are supported:
- LCT_GREY = 0, # greyscale: 1,2,4,8,16 bit - LCT_GREY = 0, # greyscale: 1,2,4,8,16 bit
- LCT_RGB = 2, # RGB: 8,16 bit - LCT_RGB = 2, # RGB: 8,16 bit
- LCT_PALETTE = 3, # palette: 1,2,4,8 bit - LCT_PALETTE = 3, # palette: 1,2,4,8 bit
- LCT_GREY_ALPHA = 4, # greyscale with alpha: 8,16 bit - LCT_GREY_ALPHA = 4, # greyscale with alpha: 8,16 bit
- LCT_RGBA = 6 # RGB with alpha: 8,16 bit - LCT_RGBA = 6 # RGB with alpha: 8,16 bit
both interlaced and non-interlaced mode supported both interlaced and non-interlaced mode supported
@ -25,17 +29,17 @@ unknown chunks will be handled properly
the following chunks are supported (generated/interpreted) by both encoder and decoder: the following chunks are supported (generated/interpreted) by both encoder and decoder:
- IHDR: header information - IHDR: header information
- PLTE: color palette - PLTE: color palette
- IDAT: pixel data - IDAT: pixel data
- IEND: the final chunk - IEND: the final chunk
- tRNS: transparency for palettized images - tRNS: transparency for palettized images
- tEXt: textual information - tEXt: textual information
- zTXt: compressed textual information - zTXt: compressed textual information
- iTXt: international textual information - iTXt: international textual information
- bKGD: suggested background color - bKGD: suggested background color
- pHYs: physical dimensions - pHYs: physical dimensions
- tIME: modification time - tIME: modification time
the following chunks are parsed correctly, but not used by decoder: the following chunks are parsed correctly, but not used by decoder:
cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
@ -52,7 +56,7 @@ Supported color conversions:
- streaming for progressive loading - streaming for progressive loading
## Basic Usage ## Basic Usage
```nimrod ```Nim
import nimPNG import nimPNG
let png = loadPNG32("image.png") let png = loadPNG32("image.png")
@ -66,7 +70,7 @@ let png = loadPNG32("image.png")
if you already have the whole file in memory: if you already have the whole file in memory:
```nimrod ```Nim
let png = decodePNG32(raw_bytes) let png = decodePNG32(raw_bytes)
#will do the same as above #will do the same as above
``` ```

2
tests/test_apng.nim
View File

@ -50,7 +50,7 @@ proc convert(dir: string) =
proc generateAPNG() = proc generateAPNG() =
const numFrames = 7 const numFrames = 7
var frames: array[numFrames, PNGResult] var frames: array[numFrames, PNGResult[string]]
for i in 0..<numFrames: for i in 0..<numFrames:
frames[i] = loadPNG24("tests" / "apng" / "raw" / "frame" & $i & ".png") frames[i] = loadPNG24("tests" / "apng" / "raw" / "frame" & $i & ".png")

14
tests/test_codec.nim
View File

@ -560,7 +560,7 @@ proc testColorKeyConvert() =
var png = s.decodePNG() var png = s.decodePNG()
var info = png.getInfo() var info = png.getInfo()
var image2 = png.convert(LCT_RGBA, 8) var image2 = convert(png, LCT_RGBA, 8)
assertEquals(32 , info.width) assertEquals(32 , info.width)
assertEquals(32 , info.height) assertEquals(32 , info.height)
@ -601,7 +601,7 @@ proc colorConvertTest(bits_in: string, colorType_in: PNGcolorType, bitDepth_in:
let modeIn = newColorMode(colorType_in, bitDepth_in) let modeIn = newColorMode(colorType_in, bitDepth_in)
let modeOut = newColorMode(colorType_out, bitDepth_out) let modeOut = newColorMode(colorType_out, bitDepth_out)
var actual = newString(expected.len) var actual = newString(expected.len)
convert( convertImpl(
actual.toOpenArray(0, actual.len-1), actual.toOpenArray(0, actual.len-1),
image.toOpenArray(0, image.len-1), image.toOpenArray(0, image.len-1),
modeOut, modeIn, 1) modeOut, modeIn, 1)
@ -710,9 +710,9 @@ proc testColorConvert2() =
modeOut.colorType = cmb.colorType modeOut.colorType = cmb.colorType
modeOut.bitDepth = cmb.bitDepth modeOut.bitDepth = cmb.bitDepth
convert(input.toOpenArray(0, input.len-1), eight.toOpenArray(0, eight.len-1), modeIn, mode_8, 3 * 3) convertImpl(input.toOpenArray(0, input.len-1), eight.toOpenArray(0, eight.len-1), modeIn, mode_8, 3 * 3)
convert(output.toOpenArray(0, output.len-1), input.toOpenArray(0, input.len-1), modeOut, modeIn, 3 * 3) #Test input to output type convertImpl(output.toOpenArray(0, output.len-1), input.toOpenArray(0, input.len-1), modeOut, modeIn, 3 * 3) #Test input to output type
convert(eight2.toOpenArray(0, eight2.len-1), output.toOpenArray(0, output.len-1), mode_8, modeOut, 3 * 3) convertImpl(eight2.toOpenArray(0, eight2.len-1), output.toOpenArray(0, output.len-1), mode_8, modeOut, 3 * 3)
assertEquals(eight, eight2) assertEquals(eight, eight2)
#tests that there are no crashes with auto color chooser in case of palettes with translucency etc... #tests that there are no crashes with auto color chooser in case of palettes with translucency etc...
@ -759,7 +759,7 @@ proc doRGBAToPaletteTest(palette: openArray[int], expectedType = LCT_PALETTE) =
s.setPosition 0 s.setPosition 0
var png2 = s.decodePNG() var png2 = s.decodePNG()
var info = png2.getInfo() var info = png2.getInfo()
var image2 = png2.convert(LCT_RGBA, 8) var image2 = convert(png2, LCT_RGBA, 8)
assertEquals(image2.data, image) assertEquals(image2.data, image)
@ -908,7 +908,7 @@ proc testAutoColorModel(colors: string, inbitDepth: int, colorType: PNGcolorType
s.setPosition 0 s.setPosition 0
var raw = s.decodePNG() var raw = s.decodePNG()
var info = raw.getInfo() var info = raw.getInfo()
var decoded = raw.convert(LCT_RGBA, inbitdepth) var decoded = convert(raw, LCT_RGBA, inbitdepth)
assertEquals(num , info.width) assertEquals(num , info.width)
assertEquals(1 , info.height) assertEquals(1 , info.height)