Use higher-resolution image data in SWTGraphics if available #922 #925
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…gef#922 When drawing an image on a scaled `Graphics` object, the image data at 100% zoom is taken and then artificially up-scaled. This results in blurry images when scaling by high factors. This change adapts the `FileImageDataProvider` and the `SWTGraphics` to take this problem into consideration, especially when dealing with SVGs. The `FileImageDataProvider` is currently not able to return the `ImageData` at arbitrary zoom levels, as this is not supported by SWT, which requires the `ImageFileNameProvider` (or the internal `ImageDataAtSizeProvider`) to be implemented. The problem with the `ImageFileNameProvider` is that it can only return proper file paths. So if an image is embedded inside a jar, it first needs to be extracted into a temporary file. The `SWTGraphics` then needs to use the new `drawImage(Image,int,int,int,int)` method so that SWT uses this provider to probler scale the image to the correct size.
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Screencast_20251222_182403.webm |
ptziegler
commented
Dec 22, 2025
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| if (transform == null) { | ||
| gc.drawImage(srcImage, x + translateX, y + translateY); | ||
| } else { | ||
| float[] transformElements = new float[6]; | ||
| transform.getElements(transformElements); | ||
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| float scaleHor = transformElements[0]; | ||
| float scaleVer = transformElements[3]; | ||
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| if (scaleHor == 1.0 && scaleVer == 1.0) { | ||
| gc.drawImage(srcImage, x + translateX, y + translateY); | ||
| return; | ||
| } | ||
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| ImageData srcImageData = srcImage.getImageData(100); | ||
| int scaledX = (int) ((x + translateX) * scaleHor); | ||
| int scaledY = (int) ((y + translateY) * scaleVer); | ||
| int scaledWidth = (int) (srcImageData.width * scaleHor); | ||
| int scaledHeight = (int) (srcImageData.height * scaleVer); | ||
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| transform.scale(1 / scaleHor, 1 / scaleVer); | ||
| gc.setTransform(transform); | ||
| try { | ||
| gc.drawImage(srcImage, scaledX, scaledY, scaledWidth, scaledHeight); | ||
| } finally { | ||
| transform.scale(scaleHor, scaleVer); | ||
| gc.setTransform(transform); | ||
| } | ||
| } |
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It's probably safer to add a new drawImage(Image,int,int,int,int) method, rather than changing the behavior of an existing method.
azoitl
reviewed
Dec 22, 2025
| float[] transformElements = new float[6]; | ||
| transform.getElements(transformElements); | ||
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| float scaleHor = transformElements[0]; |
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For #926 I brushed up my knowledge on vector math and transformation matrices. If you want to be correct in cases when rotation is applied then you need to take the elements 1 and 2 also into account.
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When drawing an image on a scaled
Graphicsobject, the image data at 100% zoom is taken and then artificially up-scaled. This results in blurry images when scaling by high factors.This change adapts the
FileImageDataProviderand theSWTGraphicsto take this problem into consideration, especially when dealing with SVGs.The
FileImageDataProvideris currently not able to return theImageDataat arbitrary zoom levels, as this is not supported by SWT, which requires theImageFileNameProvider(or the internalImageDataAtSizeProvider) to be implemented. The problem with theImageFileNameProvideris that it can only return proper file paths. So if an image is embedded inside a jar, it first needs to be extracted into a temporary file.The
SWTGraphicsthen needs to use the newdrawImage(Image,int,int,int,int)method so that SWT uses this provider to probler scale the image to the correct size.