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* Copy from go1.17 image package * Remove unnecessary files * Reduce memory usage * Add examples/ili9341/slideshow * image: add ./image/README.md * image: change convert2bin to . /cmd * Makefile: add ./cmd to NOTEST
61 lines
1.7 KiB
Markdown
61 lines
1.7 KiB
Markdown
# tinygo.org/x/drivers/image
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This is an image package that uses less RAM to run on a microcontroller.
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Unlike Go's original image package, `image.Decode()` does not return `image.Image`.
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Instead, a callback can be set to process the data corresponding to the image.
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## How to use
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First, use `SetCallback()` to set the callback.
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Then call `png.Decode()` or `jpeg.Decode()`.
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The callback will be called as many times as necessary to load the image.
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`SetCallback()` needs to be given a Buffer to handle the callback and the actual function to be called.
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The `data []uint16` in the callback is in RGB565 format.
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The `io.Reader` to pass to `Decode()` specifies the binary data of the image.
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```go
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func drawPng(display *ili9341.Device) error {
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p := strings.NewReader(pngImage)
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png.SetCallback(buffer[:], func(data []uint16, x, y, w, h, width, height int16) {
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err := display.DrawRGBBitmap(x, y, data[:w*h], w, h)
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if err != nil {
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errorMessage(fmt.Errorf("error drawPng: %s", err))
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}
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})
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return png.Decode(p)
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}
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```
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```go
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func drawJpeg(display *ili9341.Device) error {
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p := strings.NewReader(jpegImage)
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jpeg.SetCallback(buffer[:], func(data []uint16, x, y, w, h, width, height int16) {
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err := display.DrawRGBBitmap(x, y, data[:w*h], w, h)
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if err != nil {
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errorMessage(fmt.Errorf("error drawJpeg: %s", err))
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}
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})
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return jpeg.Decode(p)
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}
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```
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## How to create an image
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The following program will output an image binary like the one in [images.go](./examples/ili9341/slideshow/images.go).
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```
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go run ./cmd/convert2bin ./path/to/png_or_jpg.png
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```
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## Examples
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An example can be found below.
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Processing jpegs requires a minimum of 32KB of RAM.
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* [./examples/ili9341/slideshow](./examples/ili9341/slideshow)
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